Bluray players are down to $70au at cheap sites, DVD players are about $30au.
Bluray playback is certainly within the affordability realm of most people in western society.
Bluray's are still ludicrously priced here. Some bluray's are debuting at up to $45au, but typically $30-35. Many "catalogue title" blurays are in the $10 bargain bins.
Some DVD's are still debuting at $35, but typically $25-30, and catalogue titles are in the $5 bins.
Given the rediculous price gouging in Australia, Ebay.co.uk / Ebay.com can 1/2 the above prices.
Knowing that the future is HiDef, the bluray is certainly the better purchase.
I can only assume people are buying ludicrous quantities of movies, for the price difference to be affecting them.
4K & 8K are currently gimmicks, much like 3D was several years ago, but now 3D is pretty much mainstream and nearly every TV on retail shelves can do 3D in some form, whether you use it or not.
4K and 8K will take over. My only concern is Bluray transfer rates. Forcing 4K/8K UHD video onto bluray will limit the quality you can get out of your movies.
4x or 16x the 1080p resolution, even with a 2x improved compression ratio (good luck with that) still means you need 2x (8x) the storage & transfer rates of 1080p. Noting that most decent HQ movies do not fit on a 25GB disc, but overflow upto 35GB, that means that 4K (with a much improved compression algortihm @ 2x) will need 70GB & 2x .. ok, so that's do-able with a triple/quad layer Bluray.
And now the reality check. a 2x increase in compression ratio, while maintaining the same quality as current 1080p is very unlikely!